Energy
The introduction has stressed the need for a reduction in the use of
energy in buildings; where the part played by a strategic role for
daylighting can provide considerable savings in energy, and therefore of
carbon dioxide emissions, leading to a reduction in greenhouse gases and
ultimately a reduction in global warming.
This is now recognized by most governments, though there is still a
reluctance to take sufficient measures to overcome the problems
involved. The ‘fossil fuels’ which provide the bulk of the energy we
use at present, are still thought of as cheap alternatives to action, ignoring
the fact that coal, gas, and oil are a finite resource with limited life for the
future, leading to a potential energy crisis.
Even where this is acknowledged, most governments have not put the
necessary investment into alternative forms of energy, by developments
in the fields of wave, wind or solar power. In the past there have been
exceptions; one being in the development of hydroelectric power, where
conditions have permitted and lucky the countries which have benefitted;
another is in the use of solar power in certain countries which have
exploited their natural environment; this is an area where a developing
technology can play an important part in the future.
Nuclear power in the UK has not proved to be the answer, unlike early
projections from journalists that energy would become almost free. The
generation of energy by means of nuclear power stations, has become too
expensive, added to the unsolved problems of the disposal of nuclear
waste, to a point where it is unlikely using present technology for nuclear
to provide the alternative to fossil fuels; the development of nuclear
energy is more an issue for the environmentalist. There are countries,
such as France, where a large part of their energy is derived from nuclear
plants, but in the UK there does not at present seem to be either the will
or the means.
The future therefore appears to lie in the development of alternative
sources of energy, but the problem facing us today is in taking action to
ameliorate the energy crisis as it exists.
The reduction in the use of energy in buildings has been identified as a
major objective, of which electrical energy for lighting is a significant factor.
Lighting accounts for between a third and a half of the energy use in
commercial buildings and significant savings in energy can be obtained
where the positive use of daylight has been planned; associated with
control systems, by means of ‘daylight linking’, natural light provides the
major light source during the day with variable artificial light as back-up.
It will be found that in many of the Case Studies mentioned later in the
book, daylight has provided the necessary amount of light for large parts
of the building during the day, whilst providing the interior space with
an overall impression of daylight, even in areas where the actual daylight
factors may be relatively low, allowing light from artificial sources to be
reduced, with consequent savings in energy.
ARTIFICIAL LIGHT
All forms of energy use in buildings should be analysed, related to the
different needs of individual architectural programmes, to see where
savings can be made; for example in homes, the use of the natural source
has always been paramount during the day, so few savings can be made.
At night however, developments in lamp technology have produced
significantly more efficient artificial light sources and this is an area
where, due to the large quantity of residential property, significant
savings have yet to be made; moreover major energy savings in the home
are to be found in the means of heating and insulation. Table 4.1
illustrates the different aspects of the main types of lamp, providing
comparisons to assist the architect in making his choice. The different
factors identified are those of efficacy, lamp life and colour, but other
factors that must also be considered are those of cost and control.
It can be seen from the column under ‘Lamp efficiency’ that the
favourite domestic lamp – Incandescent Tungsten – has an efficiency of
only 7–14 Lm/watt, whilst the compact fluorescent (CFC) has an
efficiency of between 40–87 Lm/watt. At present the CFC lamps cannot
be dimmed economically, but there are many areas in homes, where
dimming is not a requirement, and with satisfactory colour (2700 K) there
is no reason not to take advantage of their long life and lower wattage.
The newer generation of lower-energy lamps such as the compact and
T-5 linear fluorescent lamps can in many cases replace less efficient
incandescent sources, which can be four to eight times more efficient;
they can also have more than eight times longer lamp life. Used in
conjunction with high frequency electronic control gear further reductions
of 20 per cent in power consumption or energy savings can be
made.
To realize these gains they must relate not only to the lamp, but also to
matching this with the the correct luminaire or light fitting. It is no use
simply fitting energy-efficient lamps into inappropriate luminaires,
resulting in unsatisfactory installations; furthermore an energy efficient
scheme demands regular, consistent and informed maintenance. It may
also be cost effective in large installations to operate a system of ‘bulk
replacement’ of lamps after a specific period irrespective of how many
lamps may have failed.
In buildings for industrial use, no doubt savings may be possible in a
rigorous investigation of the plant required to run industrial processes;
but the area most likely to result in the greatest savings is in building
services, and the greatest of these will be in the lighting, where daylight is
the key.
One of the problems has been in the ‘cheap energy policy’ of
Government; there may be other good reasons for this, but it has led in
the past to a prodigal use of cheap energy, and it is only recently, with a
looming energy crisis, that government has woken up to the vital need
for savings to be made.
The first line of defence must be in avoidance of waste; for how many
times do we pass a building with every light burning in the middle of the
day when daylight is quite adequate, or after dark when the building is
largely unoccupied. The total amount of energy wasted on a daily basis
may not have been calculated, but it is considerable and arguably equals
the amount of savings which can be made in other ways.
A particular example of this might be in transport buildings where
artificial light is used all day irrespective of the level of daylight. There is
no doubt a need for the level of daylight never to drop below the
statutory design level, but this can be solved by adopting a system of
control which links artificial light to the available daylight to ensure that
the design level is maintained, whilst allowing significant reductions in
the use of artificial light, which can be off for most of the day.
DAYLIGHT
The most obvious vehicle for energy saving in buildings is in exploiting
the most abundant source of light available to us – daylight. Environmentally
conscious assessments of building design are recognizing that
daylight (and natural fresh air) is an important commodity and should be
exploited to the full. Generally, people when asked, always prefer to
work in a daylit environment. There is a growing acknowledgement that
daylight produces positive effects, both physiological and psychological.
Forms of control are necessary to limit the potentially excessive levels
of daylight, if it is not to become a nuisance, particularly on bright sunny
days. A wide range of devices are available, from relatively inexpensive
and simple internal blinds (roller, venetian etc.) through to high tech,
computer-controlled heliodens, which track the sun.
Whilst a daylighting strategy will be needed in those buildings where a
decision to provide air-conditioning has been adopted, it is in those
buildings described as ‘passive’ where the greatest savings can be made.
A passive building is one in which the greatest use is made of natural
resources . . . natural light, solar power and ventilation derived from
making use of the natural environment. Nature cannot provide all that is
necessary, and even during the day there may well be a need for some
additional energy use, in terms of lighting from artificial sources, or
ventilation from some form of fan assistance, whilst in terms of solar
power, this can be used to advantage.
CONTROLS
The careful introduction of lighting controls can ensure that the
maximum use is made of the available daylight; so that the amount of
artificial light is reduced automatically when all, or most of it, is no longer
required to meet the design level.
The term ‘daylight linking’ has been used already, and this perhaps
needs some explanation. It is used in the sense that the artificial lighting
in a building is planned and controlled to support the natural light
40 Daylighting: Natural Light in Architecture
available during the day, to ensure that the combined lighting level meets
the desired design level.
This can be done by planning the artificial lighting circuits so as to
allow control by simple switching, so that those sources close to the
window may be switched on only when required. Such unsophisticated
means of control suffer from the human factor, in that once the artificial
light close to the window is switched on it tends to be left on all day.
A more sophisticated method known as Permanent Supplementary
Artificial Lighting (PSALI) was proposed by Prof. Hopkinson in the late
1950s; the first practical application of the technique being developed for
the Esso Building (see Lighting Modern Buildings, p. 89) where there was
dual switching for day and night, with the same lamp energy used
throughout, but using the daylight available close to the windows to
achieve the required design level when available. This still relied on the
human factor to turn on the switch.
One of the greatest advances in the technology of lighting is in the
development of modern control systems. These will be associated with
light fittings which can react by photocell to the level of daylight available
outside, enabling the design level to be maintained throughout the day,
but offering considerable savings in energy.
The control system should be appropriate to the occupation of a space,
and in a leaflet published by the British Research Establishment, Watford,
UK, the following are identified.
1. Variable occupation. Occupants spend part of their time in the space,
and part elsewhere, e.g. an office
2. Intermittent scheduled occupation, a meeting room
3. Full occupation, reception area
4. Intermittent occupation, storeroom areas.
Before deciding on the appropriate type of control it is useful to
analyse the type of ‘occupation’ as above, as this may help to determine
the nature of the control system.
It is unnecessary to dwell on the many types of control system, from
‘intelligent’ light fittings which react automatically to the ambient light
level, adjusting the total light to meet the design level; to systems where
each fitting may be controlled individually by an occupant to meet his or
her needs by means of a manual controller, or groups of fittings which
can be controlled by means of proximity switches, reacting to an
occupant’s presence.
It should be emphasized that the control system for a particular
building or part of a building should be appropriate for its use, for
example the control system for a church will be very different to that of
an office or a factory. Each programme should be analysed and those
areas of buildings where there is intermittent use, such as storage or
warehouse, need to be provided with an appropriate control regime; if
daylight is available, artificial light may not be required during the day at
all, or by some means of occupancy or proximity switching.
Control systems are at the heart of energy savings, and daylight linking
is an essential part of the solution, and may be linked into the BEMS
(Building Energy Management System).
Energy 41
SOLAR
There are two distinct aspects to the question of the relationship of
energy to the power of the sun. First there is the heat gain from the sun to
those surfaces of the building which are insolated, for the most part on
the south elevation but with some additions to east and west. This can be
a useful addition to the heating of the building in the winter, but on the
obverse side can produce overheating in the summer, which must be
dealt with.
This however is not a matter to be dealt with under the heading of
daylighting, it being more concerned with the heating and ventilation
equation.
The second aspect, is very much one of daylighting; that of the use of
the sun to generate power by means of solar panels or photovoltaics, this
is an aspect of the relationship of the sun to energy, and a growing
technology.
Despite the fact that we lack the climate to provide large quantities of
solar power (as for example in Israel, where solar panels generating
power are the rule on properties rather than the exception) the
conversion of the sun’s energy into useful power has been shown to be
effective.
The building industry has a long way to go before the technology
already available makes a substantial impact, but as the energy crisis
becomes closer the means will be found (see Lighting Modern Buildings,
Case Study No. 11. The Solar Office at Doxford International Business
Park). It has been shown that some 30 per cent of the energy required for
an office building can be provided by means of photovoltaic panels,
provided that the orientation and construction of the building has been
planned for it.
LEGISLATION
Up to the twenty-first century little effort had been made to limit the
amount of energy used for the lighting of buildings by legislation; but a
start was made by Part L of the Building Regulations of 1995, dealing with
the conservation of fuel and power; this was a start to limiting the
amount of energy used for lighting in buildings, and this coupled with
the increased efficacy of the lamps and light fittings available from the
lighting industry, had a material effect upon the energy demand.
In 2002, revisions to Part L made it a requirement to consider the need
for ‘energy efficient lighting’ more seriously, and architects should be
aware of the current regulations, which in themselves will no doubt be
further updated and modified, to increase the need for further energy
savings for the future.
The new Part L requires that ‘Reasonable provision shall be made for
the conservation of fuel and power in buildings other than dwellings, by
. . . installing in buildings artificial lighting systems which are designed
and constructed to use no more fuel and power than is reasonable in the
circumstances and making reasonable provision for controlling such
systems’. There is some flexibility for lighting designers to comply with
the regulations, and there is every reason for the spirit of the regulations
to be wholeheartedly adopted.
The regulations are divided into two parts, the first (Part L1) dealing
with dwellings, and the second (Part L2) with non-domestic buildings.
42 Daylighting: Natural Light in Architecture
The latter takes in offices, industrial buildings and those of multiresidential
use, such as hotels, hostels, old people’s homes, hospitals and
boarding schools. This is a very broad sweep of the majority of buildings,
and architects should be aware of the implications . . . it will not be
sufficient to say that your client has demanded illumination levels of 1000
lux in a hotel foyer when to provide this level the amount of energy used
is far in excess of the amount allowed for this type of space.
To give an example of the legislation the following is a quotation from
Part L2: This refers to general lighting efficiency in office, industrial and
storage buildings:
1.43 Electric lighting systems serving these buildings should be provided
with ‘reasonably efficient lamp/luminaire combinations.’ A
way of meeting the requirements would be to provide lighting
with an initial efficacy averaged over the whole building of not
less than 40 luminaire-lumens/circuit watt. This allows considerable
design flexibility to vary the light output ratio of the luminaire, the
luminous efficacy of the lamp, or the efficiency of the control gear.
Whilst this clearly precludes the use of tungsten lamps for general use,
they can still be used in some areas which may demand their use; where
the average over the whole building does not exceed the predetermined
40 luminaire-lumens/circuit watts . . . there is flexibility.
A major difference in the new regulations is that they apply to display
lighting, defined as ‘lighting designed to highlight displays of exhibits or
merchandise.’ (Examples of display lighting are included in the Case
Studies shown later, a good example being the Sainsbury Store in
Greenwich (Case Study pp. 164–167) where high levels of environmental
lighting are available during the day by the use of natural light from roof
lights, but where in terms of Part L the overall energy use is below the
limits of the requirements.)
Part L of the building regulations encourages the use of daylight
linking, stressing the relationship between the available daylight, and
controlled artificial light sources. Daylighting can be at the heart of
energy savings in buildings, and whilst in the early twentieth century this
was largely forgotten, at the beginning of the twenty-first it has been
shown to be a key to the future.
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